Construction Panel Having Improved Fixing Strength

ABSTRACT

A plasterboard comprising a gypsum matrix having wood particles embedded therein in an amount of at least 2 wt % relative to the gypsum, the gypsum matrix further comprising glass fibres in an amount of at least 1 wt % relative to the gypsum.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to, and is a continuation of,co-pending application Ser. No. 16/988,773, filed on Aug. 10, 2020,entitled “Construction Panel Having Improved Fixing Strength,” which isa continuation of application Ser. No. 15/527,128, filed on May 16,2017, entitled “Construction Panel Having Improved Fixing Strength,”which itself is the U.S. National Stage entry of InternationalApplication No. PCT/GB2015/053534, filed Nov. 19, 2015, which claimspriority to GB Application No. 1420678.3, filed Nov. 20, 2014. Theseprior applications are incorporated herein by reference in theirentirety.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to panels for use in buildingconstruction. In particular, the present invention relates to panels forproviding partitions to which items such as sinks, televisions, orradiators may be affixed.

Background to the Invention

Light-weight panels such as plasterboard (e.g. gypsum plasterboard),polystyrene board and fibreboard are commonly used to provide partitionswithin buildings. Their advantages for this application include the factthat they are light and quick to install.

However, in certain cases, such light-weight panels may have thedrawback that they are not strong enough to support fixtures (e.g.sinks, televisions, radiators, fire extinguishers, shelves and any otheritem that requires attachment to the panel). In such cases, the weightof the fixture may cause the fixing means (e.g. screws) to be pulled outof the panel, such that the fixture falls away from the partition.

This problem has previously been addressed by gluing a polymer-basedbacking lamina to one face of the plasterboard, the backing lamina beinge.g. PVC, HDPE, Nylon, polycarbonate, Bakelite, polypropylene, acetal,or fibreglass.

SUMMARY OF THE INVENTION

It has now been found that by including wood products and a polymericadditive in the plasterboard, the plasterboard may be provided withsufficient ability to retain fixing means that no backing lamina isrequired.

Therefore, in a first aspect, the present invention may provide aplasterboard comprising a gypsum matrix having particles of agglomeratedfibres embedded therein in an amount of at least 1 wt % relative to thegypsum, the gypsum matrix further comprising a polymeric additive, thepolymeric additive being present in an amount of at least 1 wt %relative to the gypsum;

wherein

no backing lamina is attached to either face of the plasterboard.

By omitting a backing lamina, it may be possible to provide a panelhaving adequate fixing strength at a relatively lower cost, due toreduced raw material costs and greater ease of manufacture.Additionally, the panel may be easier to recycle, since the requirementto separate the lamina from the plasterboard may be avoided.

The term “lamina” is intended to cover polymer-based sheets having athickness of at least 1 mm (for example 2 mm), comprising substantiallyPVC, HDPE, Nylon, polycarbonate, Bakelite, polypropylene, acetal, orfibreglass. The term “lamina” is used herein to refer to a sheet that isattached to a face of a plasterboard, e.g. by gluing, such that there isa defined interface between the plasterboard and the sheet. Thus, theterm “lamina” is not intended to refer to objects that are partially orwholly embedded within the plasterboard.

Although no lamina is attached to either face of the plasterboard, theplasterboard may have paper facings on one or both sides thereof. Inother cases, the plasterboard may have a mat partially or fully embeddedat its surface, for example, a glass fibre mat.

Typically, the particles are present in an amount of at least 2 wt %relative to the gypsum, preferably at least 2.5 wt %. Typically, theparticles are present in an amount of less than 10 wt % relative to thegypsum, preferably less than 8 wt %.

The particles may be, for example, wood particles (such as woodchip orfine sawdust particles) or paper particles. Preferably the particles arewood particles. In general, the particles are irregular in shape.

For the avoidance of doubt, the term “wood particles” is not intended torefer to particles of wood-derived material (such as paper particles)that have been processed to the point where individual fibres are nolonger bound by the natural binders present in wood.

Typically these particles have a length that is greater than 0.5 mm. Ingeneral, these particles have a length that is less than 25 mm,preferably less than 20 mm.

Typically, these particles have a thickness than is less than 4 mm,preferably less than 3 mm. In the case that the particles are paperparticles, their thickness is typically less than 0.5 mm.

In certain embodiments, the particles may be wood particles and theplasterboard may further comprise glass fibres. In such cases, the glassfibres are preferably present in an amount of at least 1 wt %.

Typically, the polymeric additive is present in an amount of at least 2wt % relative to the gypsum, preferably at least 4 wt %.

Typically, wherein the polymeric additive is selected from groupcomprising polyvinyl acetate, poly vinyl acetate-ethylene co-polymer,polyvinyl pyrrolidone crosslinked with polystyrene sulfonate, polyvinylalcohol, methyl cellulose, hydroxyethyl methyl cellulose,styrene-butadiene copolymer latex, acrylic ester latex, acryliccopolymer latex, polyester resin, epoxy resin, polymethyl methacrylate,polyacrylic acid, cationic starch, ethylated starch, dextrin andmixtures thereof.

Preferably, the polymeric additive is one of polyvinyl acetate andstarch.

In certain cases, the starch may be a native starch (that is, anunmodified starch). In other cases, the starch may be a modified starch,for example, an acid-thinned starch.

Most preferably, the polymeric additive is polyvinyl acetate.

In a second aspect, the present invention may provide a plasterboardcomprising a gypsum matrix having wood particles embedded therein in anamount of at least 2 wt % relative to the gypsum, the gypsum matrixfurther comprising glass fibres in an amount of at least 1 wt % relativeto the gypsum.

Typically, no backing lamina is attached to either face of theplasterboard.

The term “lamina” is intended to cover polymer-based sheets having athickness of at least 1 mm (for example 2 mm), comprising substantiallyPVC, HDPE, Nylon, polycarbonate, Bakelite, polypropylene, acetal, orfibreglass. The term “lamina” is used herein to refer to a sheet that isattached to a face of a plasterboard, e.g. by gluing, such that there isa defined interface between the plasterboard and the sheet. Thus, theterm “lamina” is not intended to refer to objects that are partially orwholly embedded within the plasterboard.

Although no lamina is attached to either face of the plasterboard, theplasterboard may have paper facings on one or both sides thereof. Inother cases, the plasterboard may have a mat partially or fully embeddedat its surface, for example, a glass fibre mat.

In general, the wood particles are irregular in shape.

Typically the wood particles have a length that is greater than 0.5 mm.In general, these particles have a length that is less than 25 mm,preferably less than 20 mm.

Typically, the wood particles have a thickness than is less than 4 mm,preferably less than 3 mm.

In certain embodiments of the first or second aspects of the invention,the plasterboard has paper facings. These paper facings may compriseboth cellulose fibres and glass fibres, as this is thought to improvethe fire resistance of the plasterboard. In other cases, theplasterboard may have a mat partially or fully embedded at its surface,for example, a glass mat.

In certain embodiments of the first or second aspects of the invention,the gypsum matrix comprises a hydrophobic additive, such as silicone oilor wax.

In certain embodiments of the first or second aspects of the invention,the gypsum matrix may contain a biocide.

In certain embodiments of the first or second aspects of the invention,the gypsum matrix may contain an anti-shrinkage agent such as unexpandedvermiculite, microsilica, and/or clay, in order to improve thefire-resistance of the product.

Certain embodiments of the first or second aspects of the invention mayinclude foam or lightweight aggregate such as perlite. Such additivesare known in the art to produce lower-density boards having acceptablethickness.

DETAILED DESCRIPTION

The invention will now be described by way of example only.

Gypsum plasterboards were prepared using the following generalmethodology:

Stucco and other dry additives (including woodchips) were weighed into abag and shaken to mix them. Water and wet additives were weighed into abowl and mixed using an electric mixer for 60 s.

The dry powdered additives were added to the wet additives in the bowland mixed in with the electric mixer for 30 s.

The resultant slurry was sandwiched between two sheets of paper linerand allowed to hydrate for 25 minutes measured from the time of mixing.The board was then dried in an oven for 1 hour at 160° C.

The panels had a thickness of 12.5 mm.

Comparative Example 1

A gypsum plasterboard was prepared from a slurry containing thefollowing ingredients:

-   -   stucco;    -   woodchips in an amount of 3 wt % relative to the stucco. The        woodchips had a maximum dimension in the range 1-20 mm and a        thickness of 0.5-3 mm;    -   corn starch (Merifilm from Tate & Lyle) in an amount of 6 wt %        relative to the stucco.

Comparative Example 2

A gypsum plasterboard was prepared from a slurry containing thefollowing ingredients:

-   -   stucco;    -   woodchips in an amount of 3 wt % relative to the stucco. The        woodchips had a maximum dimension in the range 1-20 mm and a        thickness of 0.5-3 mm;    -   polyvinyl acetate (Vinamul 8481) in an amount of 6 wt % relative        to the stucco.

Example 1

A gypsum plasterboard was prepared from a slurry containing thefollowing ingredients:

-   -   stucco;    -   woodchips in an amount of 3 wt % relative to the stucco. The        woodchips had a maximum dimension in the range 1-20 mm and a        thickness of 0.5-3 mm;    -   corn starch (Merifilm from Tate & Lyle) in an amount of 12 wt %        relative to the stucco;

glass fibres in an amount of 2 wt % relative to the stucco.

Example 2

A gypsum plasterboard was prepared from a slurry containing thefollowing ingredients:

-   -   stucco;    -   woodchips in an amount of 3 wt % relative to the stucco. The        woodchips had a maximum dimension in the range 1-20 mm and a        thickness of 0.5-3 mm;    -   polyvinyl acetate (Vinamul 8481) in an amount of 12 wt %        relative to the stucco;    -   glass fibres in an amount of 2 wt % relative to the stucco.

Example 3

A gypsum plasterboard was prepared from a slurry containing thefollowing ingredients:

-   -   stucco;    -   woodchips in an amount of 3 wt % relative to the stucco. The        woodchips had a maximum dimension in the range 1-20 mm and a        thickness of 0.5-3 mm;    -   glass fibres in an amount of 2 wt % relative to the stucco.

Comparative Example 3

A gypsum plasterboard was prepared from a slurry containing thefollowing ingredients:

-   -   stucco;    -   woodchips in an amount of 3 wt % relative to the stucco. The        woodchips had a maximum dimension in the range 1-20 mm and a        thickness of 0.5-3 mm.

Screw Pull-Out Strength

Screw pull-out tests were carried out on samples measuring 100 mm by 100mm that had been conditioned at a temperature of 23° C. and a relativehumidity of 50%. A 50 mm single thread wood screw was inserted into thesample, passing through a metal load transfer element positioned on thesurface of the sample. The load transfer element has a first portionthat is configured to lie between the screw head and the surface of thesample, and a second portion that is configured to engage with a testingmachine so as to allow a load to be applied to the screw along the axisof the screw. The screw was tightened to a torque of 1 Nm.

The specimen was then mounted in a Zwick Universal Testing Machine and a10N pre-load applied to the screw along the axis of the screw.Subsequently, the load was increased by setting a constant cross-headspeed of 10 mm/minute until pull out was achieved.

The results are set out in Table 1. These are averages, each taken from8 samples.

TABLE 1 Average screw pull-out Example strength Comparative 523 ± 88Example 1 Comparative 795 ± 93 Example 2 Example 1 794 ± 82 Example 21097 ± 131 Example 3 336 ± 46 Comparative 177 ± 95 Example 3

1. A plasterboard comprising a gypsum matrix having wood particlesembedded therein in an amount of at least 1 wt % relative to the gypsum,a polymeric additive distributed throughout the gypsum matrix in anamount of at least 1 wt % relative to the gypsum; wherein no backinglamina is attached to either face of the plasterboard; and furtherwherein the polymeric additive is selected from group consisting ofpolyvinyl acetate, polyvinyl acetate-ethylene co-polymer, polyvinylpyrrolidone crosslinked with polystyrene sulfonate, polyvinyl alcohol,methyl cellulose, hydroxyethyl methyl cellulose, styrene-butadienecopolymer latex, acrylic ester latex, acrylic copolymer latex, polyesterresin, epoxy resin, polymethyl methacrylate, polyacrylic acid, cationicstarch, ethylated starch, dextrin and mixtures thereof; wherein thelength of the wood particles is in the range 0.5-25 mm and the thicknessof the wood particles is less than 4 mm.
 2. A plasterboard according toclaim 1, wherein the polymeric additive is present in an amount of atleast 4 wt % relative to the gypsum.
 3. A plasterboard according toclaim 1, wherein the particles are present in an amount of at least 2 wt% relative to the gypsum.
 4. A plasterboard according to claim 1,wherein the plasterboard further comprises glass fibres.
 5. Aplasterboard according to claim 4, wherein the glass fibres are presentin an amount of at least 1 wt % relative to the gypsum.
 6. Aplasterboard according to claim 1, wherein the polymeric additive ispolyvinyl acetate.
 7. A plasterboard comprising a gypsum matrix havingwood particles embedded therein in an amount of at least 2 wt % relativeto the gypsum, the gypsum matrix further comprising glass fibres in anamount of at least 1 wt % relative to the gypsum.
 8. A plasterboardaccording to claim 7, wherein the plasterboard includes opposingexterior faces and no backing lamina is attached to either of theopposed exterior faces.
 9. A plasterboard according to claim 7, whereina maximum dimension of the particles is in the range 0.5-25 mm.